Oxygen-doped carbon nanotubes with dual active cites to enhance •OH formation through three electron oxygen reduction

The electro-Fenton (EF) process generates H₂O₂ through the 2e- oxygen reduction reaction (ORR), which is subsequently activated to •OH by iron-based catalysts. To alleviate the potential risk of external Fe-based catalysts, along with metal dissolution in acidic or neutral environments, in this study we employed oxygen-doped carbon nanotubes (OCNT) as a bifunctional, metal-free cathode to establish a metal-free EF process for organic pollutant degradation. The results demonstrate that the metal-free electrode has excellent H₂O₂ accumulation (12 mg L^-1 cm^-1) and degrades sulfathiazole (STZ) with 97.05 % efficiency in 180 min with an explanation kinetic of 0.0189 min^-1. For the first time, this enhancement came from the dual active site centers in OCNT: Ⅰ) -COOH and defects active sites were responsible for H₂O₂ production, Ⅱ) then -CO triggered H₂O₂ into •OH, avoiding the introduction of metal-based catalysts. These findings suggest that the EF system with in situ oxygen-doped cathodes have great potential for treating antibiotic wastewater.